1. Filed of the Invention
The invention provides for a novel chemical/biological protection enhancement system that is relatively inexpensive, lightweight, and could be tailored for civilian and military chemical/biological applications. No chemical/biological masks currently exist that use this process for protection enhancement. The invention uses a novel system that provides for very high levels of protection in known chemical/biological environments without the use of a self-contained breathing apparatus.
2. Brief Description of Related Art
Military and commercial chemical/biological masks fall into three general categories: negative pressure, positive pressure, and self-contained. Negative pressure masks utilize one or more filtration systems to process external filtered air into the wearer's respiratory air stream. Positive pressure units circulate external filtered air into the wearer's air stream using a fan or blower to pressurize the mask and minimize the leakage potential caused by negative pressure in the mask. Self-contained systems utilize an air source to supply or recycle air using an internal or enclosed process to shield the wearer from the environment. These are ideal for very high concentration chemical/biological environments or for environments where the elements are completely unknown. Many self-contained systems provide a level of positive pressure as well.
Negative pressure masks have limited protection capabilities. Protection factor results can range from little to no protection to 100,000:1 on a fully sealed mask. Even on a good sealing mask, leaks can be generated through facial movements, foreign matter in the seals, or through higher breathing rates. Table 1 is an example of a good sealing mask on a static head form. Protection factors are quite high at reduced breathing rates but decrease as the breathing rate increases.
TABLE 1Example of the effects of increased ventilation rates on the fitfactor performance of a negative pressure respirator. Fit Factor (LogFF)Minute VolumeEyeNose18 liters/minute12223610419750 liters/minute 56583 3883585 liters/minute 27082 29775Eye = samplefrom the eye region of the respirator;nose = sample from the oronasal cavity of the respirator.
Positive pressure masks offer the potential for increased protection factors. Protection factors can range from several thousand to well over 100,000:1 on a fully sealed mask. Tables 2-4 demonstrate the potential for increased protection factor using a variety of blower flow rates. Increasing the airflow into the mask will generally increase the protection factor of the mask. However, these protection factors are still influenced by breathing rates of the individual. Tables 2-4 demonstrate how increased breathing rates can significantly reduce the performance of a positive pressure system even on a fully sealed mask. When a user breathes faster due to higher work rates, the user can exceed the flow rate of the blower causing a negative pressure in the mask and additional seal leakage. This causes a negative pressure in the mask which brings air in from the outside.
TABLE 2Mask fit factors both with and without a blower. Blower flowrates for the low, medium (med.), and high settings wereapproximately 38 L/min, 47 L/min, and 56 L/min. all datawere collected with a ventilation rate of 18 L/min.Fit Factor (LogFF)Mask ConfigurationEyeNoseUnblown Mask122236104197Mask with Blower (low)168318364675Mask with Blower (med.)161902624246Mask with Blower (high)358458447432
TABLE 3Mask fit factors both with and without a blower. All datawere collected with a ventilation rate of 50 L/min.Fit Factor (LogFF)Mask ConfigurationEyeNoseUnblown Mask5658338835Mask with Blower (low)7942627815Mask with Blower (med.)6139423880Mask with Blower (high)5643420136
TABLE 4Mask fit factors both with and without a blower. All datawere collected with a ventilation rate of 85 L/min.Fit Factor (LogFF)Mask ConfigurationEyeNoseUnblown Mask2708229775Mask with Blower (low)3817620074Mask with Blower (med.)4582824117Mask with Blower (high)4644229384
Self-contained systems can provide very high protection factors well over 100,000:1. These systems are ideal for environments where the chemical/biological concentration is extremely high or where the hazard is completely unknown. Unfortunately, these systems are very limited in capacity. Wear times can range from several minutes to several hours. They are also very heavy and bulky, frequently requiring hoses and tanks. System weights can range from several pounds to 40 or 50 pounds depending on the system capacity.
Therefore, there is a need for a chemical/biological protection system that provides enhanced chemical/biological protection over conventional negative and positive pressure systems but is not as bulky as a self-contained system. There is also a need to provide a chemical/biological protection system that is still effective when a wearer's breathing rate increases.
Therefore, an object of the present invention is to provide a system that gives enhanced chemical/biological protection over conventional systems.
Another object of the invention is to provide a system that is not as bulky as a self-contained system but is more efficient that a negative pressure or positive pressure system.
Another object of the invention is to provide a system that compensates for increased breathing rates without sacrificing chemical or biological protection to the user.
These and other objects are met with the present invention that provides an improved protection factor that is independent of the wearer's breathing rate. The invention is a viable improvement over negative and positive pressure systems and offers a more stable protection level and can be easily adapted to almost any mask system.